What material is strong, malleable, dirt fucking cheap, has a high coefficient of friction, easy to work with, amenable to additives, meets all the suspension properties we expect out of a tire, etc, and isn't bad to breathe a lot of the dust of?

Modern tires are works of material science miracle, working with dirt cheap inputs.

Even iron dust from steel on steel friction like with trains is bad for your health.

The human lungs just have bad filtration.